This protocol is a phase II, randomized, open-label trial comparing various protease inhibitor salvage therapies for patients who have experienced failure while taking nelfinavir. The study will hopefully provide information about which protease inhibitor will provide the best second line therapy for patients who have failed nelfinavir. This study will utilize the recently approved non-nucleoside efavirenz (DMP-266/Sustiva) and the investigational protease inhibitor amprenavir.